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Standard Modern 11" Utilathe Dro?
- Thread starter architect
- Start date
To be transparent, I have the DRO already, but I have not installed it yet. I want to convert the motor to 3phase with a VFD all at the same time. But it is all mapped out and just waiting for the installs and the time to do them.
I went with a 4 axis on the lathe too. But right now, I only envision installing 3 scales.
Because the scale can be damaged by exceeding the travel limits, it's my view that the design size should exceed the lathe travel. So my axial travel is a wee bit more than the carriage travel which is less than the bed length. I plan to affix the scale to the back of the bed and the read head under the saddle.
Same goes for the cross-slide travel, but the problem here is a travel that exceeds the scale mounting space. So you may need to add an extension to the cross-slide to accommodate the additional scale length needed. There is also location to consider. A scale on the chuck side of the cross-slide is exposed to extreme damage from flying swarf and/or parts that get parted off, and/or parts that come loose. So I didnt want a scale on that side. A scale on the tailstock side is the obvious answer, but I'm a bumper - I like to index my tailstock by bumping it against the cross-slide. Which raises the probability of damaging the scale. But for every challenge there are answers. I don't remember whose original idea it was, but one of the guys on here put his scale INSIDE the cross-slide! Wow! Protected, and dead nuts accurate too. That's where mine is going.
There are a million solutions for the tailstock. I'm silly enough to want to combine the tailstock and carriage travel (just like knee and quill on a mill). As far as I know, that will be a first. But it isn't required.
The bigger question is whether or not to digitize the compound travel. Doing so would facilitate angle calculations......
Anyway, I think most guys are happy with a 2 axis DRO on their lathe - carriage and cross-slide. I think that's all that's really needed anyway. The rest is mostly my morbid curiosity.
I went with a 4 axis on the lathe too. But right now, I only envision installing 3 scales.
Because the scale can be damaged by exceeding the travel limits, it's my view that the design size should exceed the lathe travel. So my axial travel is a wee bit more than the carriage travel which is less than the bed length. I plan to affix the scale to the back of the bed and the read head under the saddle.
Same goes for the cross-slide travel, but the problem here is a travel that exceeds the scale mounting space. So you may need to add an extension to the cross-slide to accommodate the additional scale length needed. There is also location to consider. A scale on the chuck side of the cross-slide is exposed to extreme damage from flying swarf and/or parts that get parted off, and/or parts that come loose. So I didnt want a scale on that side. A scale on the tailstock side is the obvious answer, but I'm a bumper - I like to index my tailstock by bumping it against the cross-slide. Which raises the probability of damaging the scale. But for every challenge there are answers. I don't remember whose original idea it was, but one of the guys on here put his scale INSIDE the cross-slide! Wow! Protected, and dead nuts accurate too. That's where mine is going.
There are a million solutions for the tailstock. I'm silly enough to want to combine the tailstock and carriage travel (just like knee and quill on a mill). As far as I know, that will be a first. But it isn't required.
The bigger question is whether or not to digitize the compound travel. Doing so would facilitate angle calculations......
Anyway, I think most guys are happy with a 2 axis DRO on their lathe - carriage and cross-slide. I think that's all that's really needed anyway. The rest is mostly my morbid curiosity.
Brent H
Ultra Member
@architect - I believe your lathe is the 11/34 so you have additional carriage travel us shorter Utilathe guys have. I was looking at a DRO for Miss Metric as I will not be adding a taper attachment (lots of DRO space 
)
Cross feed is about 7” so would need one 8” scale for that. My lathes are the 10/20 size and will travel the full 20”. I would get a 24” scale for the longitudinal feed.
) Cross feed is about 7” so would need one 8” scale for that. My lathes are the 10/20 size and will travel the full 20”. I would get a 24” scale for the longitudinal feed.
I have the CX701 by Busybee.
I currently have two out of four (five? Bear with me...) axes done: my carriage (Z) and cross-slide (X).
I have an encoder on the spindle that drives my electronic gearing. I want to pull that signal back to the DRO as well so I can use it to set the spindle position. I might get to that this morning - I have a couple of hours to spend in the shop.
The fourth axis I'm considering is on the tailstock, which will be easy enough, I just haven't gotten there. I guess I don't do enough blind drilling.
The fifth axis would be the rotation of the compound. I keep noodling at ways to get a precise measure there and short of essentially mounting a rotary table to hold the compound I'm not finding great ways to proceed at the precision levels that would make it useful.
I currently have two out of four (five? Bear with me...) axes done: my carriage (Z) and cross-slide (X).
I have an encoder on the spindle that drives my electronic gearing. I want to pull that signal back to the DRO as well so I can use it to set the spindle position. I might get to that this morning - I have a couple of hours to spend in the shop.
The fourth axis I'm considering is on the tailstock, which will be easy enough, I just haven't gotten there. I guess I don't do enough blind drilling.
The fifth axis would be the rotation of the compound. I keep noodling at ways to get a precise measure there and short of essentially mounting a rotary table to hold the compound I'm not finding great ways to proceed at the precision levels that would make it useful.
If you ever do, I wanna know all about it. Rotary magnets with quadrature sensors work pretty well, but not well enough to make the output angle really useful. Spinning yes, stationary no.
I'll look into a 2-axis with 8" and 24" dro then! I'm not smart enough to work out a 4 axis system like Susquatch@architect - I believe your lathe is the 11/34 so you have additional carriage travel us shorter Utilathe guys have. I was looking at a DRO for Miss Metric as I will not be adding a taper attachment (lots of DRO space
Cross feed is about 7” so would need one 8” scale for that. My lathes are the 10/20 size and will travel the full 20”. I would get a 24” scale for the longitudinal feed.
I'll look into a 2-axis with 8" and 24" dro then! I'm not smart enough to work out a 4 axis system like Susquatch
Oh Bull Poop. It's all just distances and angles, some math, and some trig. You architects all love angles and curves.
But seriously, 2 axis is all you really need on a lathe.
Brent H
Ultra Member
@architect - you need a longer longitudinal scale. Measure out the travel. I think you need like a 36” scale for that lathe
@architect - to measure travel properly, you need to set a reference on the moving piece (say a given corner of the saddle - doesn't really matter where as long as the same point is used for all measurements), then move the
Saddle to one extreme - (say against the head), make a reference mark on the bed adjacent to your chosen saddle point, then move the saddle to the far end as far as it will ever go. I chose to remove my tailstock and moved the carriage as far as the carriage rack will allow it to go. Make another mark on the bed and then measure between marks. This is your travel.
However, you also need to add some length for the scale end caps and for the read head. Usually, the seller will tell you what those three numbers are and in fact, they will usually add them to your travel measurements for you. The only concern here is communication errors between you and the seller. This one is worth beating to death with them to make sure you are both on the same page.
Yes, I played with some of these and the precision is just too low to align for an morse taper, for example.
I've been thinking of trying something with differential readings at either end of the slide with some built-in trig, at the cost of more encoder bulk.
I'm an idjit. One pivot, treat it like a sine bar. I'm going to try to build this tomorrow.
That is the best I could do too. But it doesn't easily lend itself to a compound that can be swung around 360 degrees. Or if it can, I couldn't see it. Too bad the rotary sensors are useless.
Worse, I'm not seeing good prospects for repeatability and rigidity with the usual pivot design.
Which brings me back to two measurements, one ahead of the pivot and one behind. And those clutter the space and get in the way of the full swing when you want to do that.
So yeah, I'm not smarter than 100 years worth of cross-slide designers.
The best I've been able to manage is an improved visual scale. I have a thread in progress on it. I damaged the mechanical scale I was working on so I ordered a new one. But the postal strike has put me in limbo. When it finally arrives, I'll finish the scale and then start working on a Vernier scale for it. Even so, I doubt that will give me more than 10ths of a degree (6 minutes).
In the meantime, I keep looking for an improved sensor. If I could build that into the top of my compound post it would be a paradigm shift.
I keep coming back to wrapping a length of mag tape around the circular base and reading that.
Mine is 3.5" in diameter, meaning 282mm circumference; with a 5um scale that means somewhere about 5*10^-5 degrees resolution, which is tenths of an arc-second.
I just don't know if I'll be able to get the tape wrapped around sufficiently uniformly and with a clean join at the looping point. I should turn up a new disk with a little overhang I can tuck the stainless sheild into as well.
And then there's all the precision questions of concentricity. I'm sure a bunch could be calibrated out.
Hmm, I wonder if they make loops of mag tape?
My turn to admit being brain dead. Never thought about a strip of magnetic tape on the compound base......
I think the main issue will be swarf. The discontinuity can simply be put where ever you know you will never use it. You will need to do a regular Calibration and I'm not sure how to do that right off the cuff. But I know at some point it could make the whole cure worse than the disease.
I think you could warm the tape before bending it.
An aluminium guard enclosure with a stainless cover could be bent and added. Easy to put the sensor behind the compound.
I'll have to read up on it, but I think my Ditron can handle the distance to angle conversion.
The incentive to do this is high. 1 micron tape would generate a very very fine angular resolution.
More to digest when I'm sleeping.
I think the main issue will be swarf. The discontinuity can simply be put where ever you know you will never use it. You will need to do a regular Calibration and I'm not sure how to do that right off the cuff. But I know at some point it could make the whole cure worse than the disease.
I think you could warm the tape before bending it.
An aluminium guard enclosure with a stainless cover could be bent and added. Easy to put the sensor behind the compound.
I'll have to read up on it, but I think my Ditron can handle the distance to angle conversion.
The incentive to do this is high. 1 micron tape would generate a very very fine angular resolution.
More to digest when I'm sleeping.
That will require a bushing on your compound base. But at least you won't have a discontinuity to deal with.
And you will still have to recalibrate every time you turn the power off and rotate the compound.
That one seems to use some other encoding rather than quadrature as it says it has 6400 pulses per rev.
And you will still have to recalibrate every time you turn the power off and rotate the compound.
That one seems to use some other encoding rather than quadrature as it says it has 6400 pulses per rev.
Not recalibrate, just re-zero. Zero is a PITA however. Though I'm imagining a jig to check against the ways somehow.